Rio's relentless expansion has been based on its long-held forecast that demand for steel in China would grow to 1 billion tonnes around 2025, matching an estimate from BHP Billiton.The company shrugged off attacks from smaller rival Fortescue Metals Group which has criticised Rio Tinto and BHP for flooding the market, driving down prices, and in turn hurting smaller miners and the Australian economy.The company shrugged off attacks from smaller rival Fortescue Metals Group which has criticised Rio Tinto and BHP for flooding the market, driving down prices, and in turn hurting smaller miners and the Australian economy.The world no.2 iron ore producer expects to ship 350 million tonnes of the steel-making ingredient this year, up from 300 in 2014.